Cosmological Spacetimes from Negative Tension Brane Backgrounds

TL;DR

This paper constructs and analyzes a class of time-dependent cosmological spacetimes derived from negative-tension branes, revealing their properties, stability, and thermodynamics, with potential implications for cosmology.

Contribution

It introduces explicit solutions of Einstein-dilaton-Maxwell theory with negative-tension branes that exhibit cosmological expansion and horizon structures, expanding understanding of such exotic configurations.

Findings

Solutions describe gravitational effects of negative-tension branes.

Spacetimes exhibit horizons and no naked singularities.

Computed brane charge, tension, and thermodynamic properties.

Abstract

We identify a time-dependent class of metrics with potential applications to cosmology, which emerge from negative-tension branes. The cosmology is based on a general class of solutions to Einstein-dilaton-Maxwell theory, presented in {hep-th/0106120}. We argue that solutions with hyperbolic or planar symmetry describe the gravitational interactions of a pair of negative-tension $q$-branes. These spacetimes are static near each brane, but become time-dependent and expanding at late epoch -- in some cases asymptotically approaching flat space. We interpret this expansion as being the spacetime's response to the branes' presence. The time-dependent regions provide explicit examples of cosmological spacetimes with past horizons and no past naked singularities. The past horizons can be interpreted as S-branes. We prove that the singularities in the static regions are repulsive to time-like geodesics, extract a cosmological `bounce' interpretation, compute the explicit charge and tension of the branes, analyse the classical stability of the solution (in particular of the horizons) and study particle production, deriving a general expression for Hawking's temperature as well as the associated entropy.